The following abbreviations are herewith defined:    3G third generation of GSM-based mobile networks    3GPP third generation partnership project    AC admission control    AF activity factor    ARP allocation/retention priority    BLER block error rate    CQI channel quality indicator    DCH dedicated channel    DL downlink (Node B to UE)    DPCH dedicated physical channel    Eb/N0 energy per bit per noise power spectral density    E-DCH enhanced UL DCH    EPBR E-DCH provided bit rate    GBR guaranteed bit rate    GSM global system for mobile communication    HC handover control    HSDPA high-speed downlink packet access    HS-DSCH high-speed downlink shared channel    HS-SCCH high-speed shared control channel    HSUPA high speed uplink packet access    Iu interconnection point between RNC or BSC and 3G core network    Iub RNC/Node B interface    Iur RNC/RNC logical interface    LC load control    MAC medium access control    MAC-hs MAC-high speed    NBAP Node B application part    Node B base station    NRT non-real time    PDP packet data protocol    PDU protocol data unit    PIE power increase estimator    PS packet scheduler    RNC radio network controller    RRM radio resource management    RT real time    SPI scheduling priority indicator    TC traffic class    THP traffic handling priority    UE user equipment, such as a mobile station or mobile terminal    UL uplink (UE to Node B)    UMTS universal mobile telecommunications system    Uu radio interface between UTRAN and UE    UTRAN universal terrestrial radio access network    VoIP voice over internet protocol    WCDMA wideband code division multiple access
When performing admission control in a system, that includes HSDPA, for a new user of a certain priority and with certain requirements, which can be expressed in GBR and maximum delay constraints, the admission control function of the RNC needs to know what the required power is of the existing users. The required power depends on the QoS requirements of the existing users. The Node B provides a required power attribute per priority class (SPI). This required power is defined as “the minimum necessary power for a given priority class to meet the Guaranteed Bit Rate for all the established HS-DSCH connections belonging to this priority class”, and assumes 100% user activity.
As can be appreciated, the RNC needs to have knowledge of the AF of the users in order to know the actual required power per SPI class.
The AF follows the user behavior and defines the percentage of the time that the user (the UE associated with the user) is active. The effective value may vary significantly among users. For certain real time services, such as VoIP, a fixed AF would be a quite accurate measure (e.g., AF=50% for conversational applications and AF=100% for streaming applications). However, the estimation of the AF becomes a non-trivial issue for non-real time (NRT) applications since the user behavior for NRT services can vary considerably and, moreover, it can depend significantly on the network status. For example, a wireless network with a low load would provide a higher user throughput for non-real time users triggering, on average, greater user activity and vice versa. In this case the actual AF might be measured in the RNC according to the data received and transmitted. However, this approach would not be adequate, as the value of AF would vary considerably depending on the averaging period that was used. It is noted that for NRT services AC can be performed in order to guarantee a minimum bit rate.